(S)-3-hydroxybutyric acid and (S)-3-hydroxylbutyrate ester are very effective chiral intermediates and have a wide range of applications such as in plastic materials, aromatics, medicines and agrichemicals (Speciality Chemicals Magazine, April:39, 2004). For example, they may be used to synthesize (S)-1,3-butanediol, an intermediate for preparing various antibiotics and pheromones by reduction of ethyl-(S)-3-hydroxybutyrate (T. Ferreira et al., Tetrahedron, 46:6311, 1990), and may be used as a precursor of a herbicide, (S)-sulcatol (K. Mori et al., Tetrahedron, 37:1341, 1981), a precursor of a b-lactam antibiotic, Carbapeneme (T. Chiba et al., Chemistry letters, 16:2187, 1987), and a precursor of a vitamin-like nutrient, L-carnitine (B. N. Zhou et al., Journal of American Chemical Society, 105:5925, 1983).
There is a conventional method for preparing ester such as asymmetric reductive hydrogenation of a prochiral precursor, 3-ketoester, with a catalyst, diphosphine-ruthenium (R. Noyori et al., Journal of the American Chemical Society, 109:5856, 1987), but this method requires a very expensive metal catalyst, a pure substrate and a very high-pressure reactor. Further, production of ethyl (S)-3-hydroxybutyrate with a yield of 58% and an optical purity of 94% ee by biocatalytic reduction of b-ketoester using yeast as a whole-cell catalyst exhibits low optical activity due to various oxidoreductases present in microorganisms (Tetrahedron Letters, 34:3949, 1993).
It has been reported that optically-active (R)-3-hydroxyalkanoate is biosynthesized from glucose by manipulating a metabolic pathway of a microorganism (Lee et al., Biotechnol Bioeng, 65:363, 1999; Lee and Lee., Appl Envron Microbiol, 69:1295, 2003; Gao et al., FEMS Microbiol Lett, 213:59, 2002). There are two routes to produce (R)-3-hydroxyalkanoate: one is autolysis of a biodegradable polymer, polyhydroxyalkanoate (Lee et al., Biotechnol Bioeng, 65:363, 1999; Lee and Lee., Appl Environ Microbial, 69:1295, 2003); and the other is removal of CoA from (R)-3-hydroxylalkanoyl CoA synthesized from glucose, not the autolysis of a biodegradable polymer, to produce (R)-3-hydroxyalkanoate (Gao et al., FEMS Microbiol Lett, 213:59, 2002). In the second route, (R)-3-hydroxybutyryl CoA is produced from glucose using β-ketothiolase (PhaA) and (R)-3-hydroxybutyryl CoA reductase (PhaB), and then CoA is removed from the (R)-3-hydroxybutyryl CoA using phosphotransbutylase (ptb) and butyrate kinase (BuK) (Gao et al., FEMS Microbiol Lett, 213:59, 2002).
While chemical and biocatalytic routes for producing optically-active (S)-3-hydroxybutyrate have been reported, a route for producing optically-active (S)-3-hydroxybutyric acid and (S)-3-hydroxybutyrate ester biosynthesized from glucose by manipulating a metabolic pathway of a microorganism had not yet been reported.
Therefore, the present inventors tried to biosynthesize optically-active (S)-3-hydroxybutyric acid and (S)-3-hydroxybutyrate ester and finally found that they are biosynthesized with high optical purity from acetyl CoA produced in glycolysis of a microorganism by a simple process involving the manipulation of a metabolic pathway by a recombinant gene introduced into the microorganism without using an expensive metal catalyst or a substrate. This discovery led them to the present invention.